I made these for my warhammer 40k chaos daemons army to use as heralds of the four gods.
Conquest (white horse) - Tzeentch herald
War (red horse) - Khorne herald
Famine (black horse) - Nurgle Herald
Death (pale horse) - Slaanesh herald
Great execution. Am working on the same concept for my 4 Venoms in my Dark Eldar army. :)
Pestilence/Conquest are the same horseman, even though there are various interpretation from various books coming from different times in history.
I have to comment since I had an idea to make a similar project. I think you have a great idea here, and the execution is very decent. Although, it would have been nice to see these ona diorama base, but i understand why not, because they are for your army :)
Oh, and for previous comment by precinctomega, the pedant in you probably should read a book called The Bible, since the four horsemen of the Apocalypse are in fact Conquest, War, Famine and Death.
A lovely idea and great execution, but the pedant in me is forced to point out that traditionally, the four horsemen are War, Famine, *Pestilence* and Death, and that Pestilence should probably be Nurgle, although Slaanesh doesn't fit easily into that categorization.